As recent electronic products are miniaturized and slimmed into various shapes, conventional rectangular parallelepiped batteries are inappropriate to efficiently use inner spaces of miniaturized and slimmed electronic products.
Thus, batteries having various shapes, such as stepped batteries, are manufactured to correspond to the shapes of battery accommodating spaces in electronic products.
Stepped batteries are formed by sequentially stacking cells, having various sizes and shapes, into a desired shape. A technology of forming a stepped battery in a stack and folding manner is disclosed (refer to Korean Patent Publication No. 2013-106781).
Although such technologies of manufacturing a stepped battery by stacking cells in a folding manner are significantly convenient and advantageous in a manufacturing process, a tent shape formed by a separation film after the manufacturing process is an issue that should be addressed.
FIG. 1 is a side view illustrating a stepped battery 10 formed in a stack and folding manner. FIG. 2 is a side view illustrating a process of accommodating the stepped battery of FIG. 1 in a pouch.
Referring to FIGS. 1 and 2, a first bi-cell (a radical unit), which is constituted by a cathode, a separator, an anode, a separator, and a cathode, and a second bi-cell (a radical unit) which is constituted by an anode, a separator, a cathode, a separator, and an anode are stacked and folded using a separation film 16 for a folding operation, thereby forming the stepped battery 10. When a stepped battery is manufactured in a stack and folding manner, small cells 14 are stacked on large cells 12 to form stepped surfaces 18 between the small cells 14 and the large cells 12, thereby forming tent shapes on the separation film 16, as illustrated in FIGS. 1 and 2 . . . . The stepped surfaces 18 may be surfaces that form stepped parts caused by a difference in size between the small cells 14 and the large cells 12.
When a tent portion of the separation film 16 is accommodated in a pouch 20 having a step shape needed for the stepped battery 10 as illustrated in FIG. 2, the tent portion interferes with the pouch 20 so as to break the separation film 16 or push the separation film 16, thereby moving stacked electrodes, which causes an additional defect.